1. Field of the Invention
The invention pertains to an improved magnetically actuated fluid motor powered by a primary fluid stream and useful for attachment to a pumping apparatus for injecting predetermined quantities of secondary fluid additive into the primary fluid stream.
2. Background of the Prior Art
It has been found that a reciprocating fluid motor can be powered by energy from a pressurized primary fluid line which is useful to drive an attached pump which injects a secondary fluid into the primary fluid stream. Such devices have been useful in applications such as adding medication to drinking water for livestock, treating water with additives such as halogens, or adding fertilizer concentrate to irrigation water. A shifter mechanism with valves carried by the piston enables the fluid pressure to be applied to either face of a stepped piston which forms the driving member for a metering piston interacting with a cylinder in communication with a storage vessel of the product to be injected. Such devices are found in my own U.S. Pat. Nos. 4,558,715 and 4,809,731, as well as U.S. Pat. No. 4,756,329 to Jean Cloup.
In conventional reciprocative fluid power motors, a sliding shaft extends through the head of a differential stepped piston, usually through the center of the piston, and extends on both sides of the piston. The shaft is connected to a toggle mechanism which controls two sets of valves to alternately close fluid passages in one stepped piston face and open a flow passage or passages in the other stepped piston face. When the piston moves up or down and responds to greater fluid pressure on one of the stepped faces, the upper or lower ends of the rods strike the housing causing the rod to stop moving while the piston continues to move. This causes relative sliding movement between the rod and the pressurized face of the piston requiring a seal therebetween to prevent the loss of pressure. It would be desirable to eliminate the need for such a seal.
The toggle mechanisms require strong springs in order to provide a sufficient "kick" to shift the rod which controls the valve members. This is necessary to ensure continued operation especially in the face of contamination over extended periods of time with aqueous solutions and contaminants. Thus, conventional designs for these pump motors have a multitude of parts which are subject to stresses, wear and corrosion which decrease the ease of assembly, disassembly and maintenance. In addition, the use of strong springs makes the conventional toggle mechanisms noisy, and the usual design makes it difficult to eliminate the noise.
It would be desirable to produce a quieter unit because pumping apparatus of this kind are frequently used in places where noise in operation may disturb people in the surrounding area. It would be desirable to have a unit with less powerful springs which in addition to reducing the noise factor, produces less wear and tear on the unit during operation. It would also be desirable to produce a unit which employs springs which operate in compression rather than tension because that makes it easier to provide secondary treatment in manufacturing which makes them less subject to breakage or corrosion and easier to install. The open coil design of a compression spring makes it possible to employ mechanical treatments and easier to reach all areas with chemical treatments. All these and more advantages are provided by the improved magnetic activated fluid motor.